Scanning probe microscope and specimen surface structure measuring method

ABSTRACT

A digital probing type atomic force microscope (AFM) for measuring high aspect structures with high precision. A probe  21  is vibrated while moved to the vicinity of an atomic force region on a specimen surface. The position of the probe is measured when a specified atomic force is detected in the atomic force region. The probe is then moved away from the specimen surface. A servo system for maintaining a gap between the probe and specimen surface is stopped. The probe is moved to a measurement point along the specimen surface while kept away from the specimen. The vibration frequency is a frequency slightly offset from the cantilever resonance point. The atomic force is detected based on the vibration amplitude of the cantilever.

TECHNICAL FIELD

The present invention relates to a scanning probe microscope capable ofmaking three-dimensional measurements on the nanometer order of accuracyon the surface structure of a specimen, and relates in particular to aprobe microscope capable of accurate measurements of a surface structurewith a fine structure on the nanometer level, and further possessing ahigh aspect ratio.

BACKGROUND ART

In recent years, along with the growth of our information society, thereare increasing needs for technology capable of joint use of largeamounts of information. The semiconductor field is making progress inminiaturization. Current leading edge technology is seeking tominiaturize devices to a minimum scale of 0.13 μm. Along with thisprogress, there is also a need for higher precision and greaterminiaturization in device isolation technology, wiring technology andcontact technology, etc. Structures with a higher aspect ratio(depth/aperture diameter) are also being proposed and technology tofabricate these structures is being sought. Besides fabricationtechnology, advances in measurement technology are also needed. Inparticular, development of methods for measuring precision on thenanometer scale are needed. More specifically, according to thesemiconductor road map for the future, the current minimum hole diameterof 180 nanometers will shrink to 60 nanometers by the year 2010. Also,aspect ratios will increase from 7 to 12 so measurement down to thesedimensions will also become increasingly difficult. Current technologyuses the scanning electron microscope (SEM), to observe a cross-sectionof the specimen after splitting it open or machining it with a focusingion beam (FIB) technology.

These types of methods using probe microscopes to measure surfacestructures with high aspect ratios include a method (U.S. Pat. No.2,936,545) for discrete scanning of the specimen in a state where theprobe is separated from the specimen, and the probe is moved to ameasurement point in proximity to the specimen to measure the surfaceposition. In this method, during scanning of the surface, the gapbetween the specimen and probe when making an actual physicalmeasurement is larger than necessary and the probe moves at high speedto the next pixel; and when making surface measurements, the scanning isstopped, and the probe is moved in proximity to the specimen andmeasures the surface position.

Measurements of a specimen surfaces with a large aspect ratio and smallaperture diameter require attaching an extremely slim probe as a tip ofthe cantilever. The elasticity (spring constant) of the probe istherefore poor horizontally and is nearly the same spring constant asthe cantilever. The probe therefore warps or deforms on reaching theoblique surface (of the specimen).

In atomic force microscopes (AFM) of the conventional art with contacttype digital probing, the probe at the pixel position, repeatedly movesclose to the specimen surface and then back. When the probe captures thespecimen surface while nearing it, and when the oblique surface issteep, the cantilever 80 and probe 81 are twisted as shown in FIG. 10,and an error appears in the position measurement on the surface of thespecimen 82. The measurement position error Ar (surface interior) and Az(perpendicular direction) are expressed as follows due to the warping ofthe probe.Δr=F _(c) tan θ/k(k=El/(5γ_(a) ³),γ_(a) =l/t)  (1)Δz=Δr tan θ  (2)F_(c)=F cos²θ  (3)

Here, F_(c) is the fixed atomic force, θ is the angle the obliquesurface tilts from perpendicular relative to the probe, k is the springconstant of the probe, E is the Young's modulus of the probe, l is theprobe length, and t is the probe thickness. The γ_(a) is here called theprobe aspect ratio. The probe aspect ratio holds roughly the samesignificance as the specimen aspect ratio. This type of measurementcannot be performed unless the probe aspect ratio is higher than thespecimen aspect ratio.

In contact type methods for detecting atomic force such as the lightdeflection method, the force setting is approximately 10⁻⁸N. Forexample, when the atomic force F_(c) setting is 10⁻⁸N, the angle θ is 45degrees, the Young's modulus E of the probe is 2×10¹¹N/cm², the probelength l is 1 μm, and the probe thickness is 50 nanometers (γ_(a)=20),then the Δr and the Δz are 2 nanometers. When the angle θ is 80 degrees,then the Δr is 11 nanometers and the Δz is 64 nanometers. Further, whenthe angle θ is 85 degrees, the Δr is 23 nanometers, the Δz is 261nanometers, it can be seen that the probe tip will slip on the specimensurface. This slippage shows that the technology of the conventional artis not capable of accurately measuring the shape of surface structureshaving a high aspect ratio.

In view of the problems with the conventional art, the present inventionhas the object of providing a scanning probe microscope capable ofaccurately measuring surface structures with high aspect ratio, and amethod for measuring surface structures of specimens having a highaspect ratio.

DISCLOSURE OF THE INVENTION

As can be seen from equations (1) and (2), lowering the atomic force Fcby regulating it to a fixed quantity with the servo will prove effectivein reducing the measurement position errors Δr and Δz. In other words,it is important that a small atomic force be used to control the system.The conventional art utilized the atomic force of the repulsive forceregion to accomplish this. However, the minimum atomic force isapproximately 10⁻⁸N so achieving a measurement position error of 1nanometer or less, requires setting an atomic force regulated to 10⁻¹⁰Nor less.

In order to regulate the atomic force to 10⁻¹⁰N or less, the presentinvention employs the vibration type force detection method. In otherwords, the present invention uses a non-contact force detection method.In this method, the cantilever supporting the probe is oscillated at itsresonance point, and the shift occurring in the resonance point(resonance frequency) due to an externally applied force is measured.There are two types of non-contact force detection methods. One type (FMmodulation type) detects the weak force acting on the probe byoscillating the cantilever supporting the probe at its resonance pointand measuring the shift in the resonance point due to an externallyapplied force. The other type (slope detection method) oscillates thecantilever at a frequency slightly shifted from its resonance point, andmeasures the minuscule atomic force by measuring the change in amplituderesulting from the externally applied force. The atomic force in theattraction force region is detected by utilizing these methods. Anatomic force of around 10⁻¹³N can be detected by these methods. Further,a probe position error of 1 nanometer or less can be attained even witha slope of 85 degrees or more on the specimen cross section so thatshapes with an aspect ratio of 10 or more can be measured with accuracyon the sub-nanometer level. High aspect probes such as carbon nanotubescan also be used as probes in this invention.

The scanning probe microscope of the present invention is in otherwords, characterized in comprising: a specimen stage for mounting thespecimen, a probe, a cantilever for supporting the probe, a first probemovement means for moving the probe two-dimensionally along the surfaceof the specimen, a second probe movement means for moving the probecloser to or farther away from the specimen surface, a probe positiondetection means for detecting the probe position, a means to oscillatethe cantilever at a specified frequency shifted slightly from thecantilever resonance point, an amplitude detection means to detect theoscillation amplitude of the specified frequency component of thecantilever, and a control means to detect changes in the vibrationamplitude while moving the cantilever closer to the specimen surface andmeasure the probe position when the change in the vibration amplitudehas reached a specified quantity. The amplitude detection means iscomprised of a lock-in amplifier.

The scanning probe microscope of the present invention is furthercharacterized in comprising: a specimen stage for mounting the specimen,a probe, a cantilever for supporting the probe, a first probe movementmeans for moving the probe two-dimensionally along the surface of thespecimen, a second probe movement means for moving the probe closer toor farther away from the specimen surface, a probe position detectionmeans for detecting the probe position, a means to oscillate thecantilever supporting the probe at that resonance point, a resonancefrequency shift detection means to detect a shift in the resonancefrequency of the cantilever, and a control means to detect a shift inthe resonance frequency of the cantilever while moving the cantilever ina direction closer to the specimen surface, and measure the probeposition when the shift in the resonance frequency reaches a specifiedquantity. The resonance frequency shift detection means may be comprisedof a phase-locked-loop circuit.

The probe of the scanning probe microscope of the present invention maybe comprised of carbon nanotube. The probe position detection means mayutilize a capacity displacement meter a strain gauge, a lightinterferometer or an optical lever.

The specimen surface structure measuring method of the present inventionfor measuring the surface structure of the specimen utilizing thescanning probe microscope containing a cantilever supporting the probe,with this measuring method comprising: a step to stop the servo systemmaintaining a fixed gap between the probe and specimen and move theprobe along the specimen surface to the measurement point with the probeseparate from the specimen, a step to oscillate and move the probe closeto the specimen surface and measure the probe position when a specifiedatomic force is detected in an attraction force region, and a step tomove the prove away from the specimen surface immediately after themeasurement, and the above steps are repeated at each measurement point.In the step to move the probe away from the specimen surface, the probeis lifted with a distance or more where there is no absorption force toattract the probe.

After the probe detects the specified atomic force, the probe is pulledback from the specimen immediately. However, the probe might sometimesstrike the specimen surface due to a circuit delay, etc. The probe mightthen break and the measurement function disabled. To avoid probebreakage, the servo circuit (circuit to control the distance between thespecimen and probe to attain the desired atomic force) preferablyutilizes a distance control signal when moving the probe in proximity tothe surface of the specimen. The probe should also preferably movetowards the specimen at a constant speed. Using the servo circuit signalto avoid the probe striking the specimen for the probe approach to thesurface is essential at this time.

More specifically, the probe vibration frequency is a frequency shiftedslightly from the resonance point of the cantilever, and the specifiedatomic force is detected based on the change in the vibration amplitudeof the cantilever.

As an alternative, the vibration frequency of the probe may be made thecantilever resonance point frequency and, the atomic force detectedbased on the shift in the cantilever resonance frequency.

The scanning probe microscope of the present invention may used formeasurement of tiny devices or may be used to measure defects. Thisscanning probe microscope may also be used as a line monitor in thesemiconductor manufacturing process. In the basic probe operation duringmeasurement, when the scanning stops the surface position is measured,and during scanning the probe is separated from the specimen surface.The vibration method (non-contact) method is used simultaneous withprobe operation at a force setting of 10⁻¹⁰N and below. Therefore, evenwith an aspect ratio of 10 or more, errors of 1 nanometer or less due toslip of the probe can be suppressed, and high precision shapemeasurement can be performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing an example of the digital probing AFMof the present invention using the slope detection method;

FIG. 2 is concept drawing showing an example of the probe of carbonnanotube;

FIG. 3 is a drawing showing the movement of the probe during ameasurement sequence in vibration type digital probing AFM;

FIG. 4 is a concept block diagram of the lock-in amplifier;

FIG. 5 is graph showing the relation of the detection amount fromchanges in amplitude by the lock-in amplifier and the distance betweenthe specimen surface and the probe;

FIG. 6 is a concept block diagram of showing another example of digitalprobing AFM in the present invention;

FIG. 7 is a block diagram of the PLL circuit;

FIG. 8 is a graph showing the interrelation of the resonance frequencydetected by the PLL circuit, and the distance between the specimensurface and probe;

FIG. 9 is a concept block diagram of the semiconductor scanning deviceof the present invention; and

FIG. 10 is a drawing describing the force acting on the probe and theprobe torsion when the probe has approached the oblique surface.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is next described in detail while referring to thedrawings. The digital probing AFM of the present invention possesses asystem to detect the force gradient. In the following drawings, sectionswith the same functions are assigned identical reference numeral andtheir redundant description is omitted.

First Embodiment

FIG. 1 is a block diagram showing an example of the digital probing AFMof the present invention using the slope detection method. In additionto the usual AFM structure, this digital probing AFM contains avibration mechanism for detecting the atomic force gradient.

The specimen 11 is mounted on the XY specimen stage 12. The XY specimenstage 12 is moved coarsely by the XY scanning circuit 25 so that themeasurement region is selected directly below the probe. The cantilever22 with the probe is attached on an exciter piezoelectric element 23 anda cylindrical XYZ scanning piezoelectric element 24. A normal opticallever method made up of a semiconductor laser 31, a position detector32, and a force detector 34 is utilized as the force detector. The servocircuit 35 drives the probe in the Z direction by means of the XYZscanning piezoelectric element 24, and servo controls the force to afixed value with the signal detected by force detector 34. The XYscanning circuit 25 performs XY scanning utilizing the XYZ scanningpiezoelectric element 24 for drive of the probe in the XY directionsalong the specimen surface. Though not shown in the drawing, an approachis installed for making the probe approach or retract from the surfaceof the specimen 11 with a large stroke from Z movement of the XYZscanning piezoelectric element 24. The present example utilizes alock-in amplifier 40 for detecting the force gradient. The controller 37controls the XY scanning circuit 24 and the servo circuit 35.

The probe preferably has a shape and slim shape as possible in view ofthe height and groove depth of the specimen 11. In particular probeswith an aspect ratio of 10 or more are preferably fabricated using acarbon nanotube or carbon fiber, etc.

FIG. 2 is concept drawing showing an example of the probe of carbonnanotube. A carbon nanotube forming the probe 21 is bonded to the tip ofthe cantilever 22 made from silicon film, silicon nitride film orsilicon oxide film. The diameter of the carbon nanotube is preferablyapproximately 10 to 50 nanometers and the length is 500 nanometers ormore. The carbon nanotube is attached to the cantilever 22 by adheringthe carbon nanotube to the tip of the cantilever supporting to amanipulator not shown in the drawing. The electron beam is thenirradiated onto the end section (arrow position in drawing) cantilever22 side of the carbon nanotube, and the bonding (adhesion) is performedby means electron beam deposition of the carbon at that time.

FIG. 3 is a drawing showing the movement of the probe during themeasurement sequence in vibration type digital probing AFM shown inFIG. 1. FIG. 3(a) is a drawing showing the repeated movement of theprobe along the specimen surface. FIG. 3(b) is a drawing showing thefundamental movement of the probe for one pixel point.

The probe 21 is first of all driven approximately a few to a few hundrednanometers in the Z direction while vibrated by the XYZ scanningpiezoelectric element 24 and is made to approach the surface of thespecimen 11. An excitation signal is at this time output from thelock-in amplifier 40 or an external oscillator, and input to the exciterpiezoelectric element 23. The vibration of the exciter piezoelectricelement 23 then vibrates the probe 21. The vibration frequency is afrequency shifted slightly from the cantilever resonance point. When thepreset atomic force gradient acts on the probe 21, the vibrationamplitude changes, and matches the value that was set. This (match) isdetermined when the probe 21 reaches to the specimen 11. The driving ofthe probe 21 towards the vicinity of the specimen surface is stopped.The probe 21 is then lifted up in a pre-determined distance ΔZ toretract it from the specimen surface (2). This distance ΔZ is at least adistance where the specimen 11 has no absorption force on the probe 2,or is set as a distance larger than the predicted surfaceirregularities. Next, at the point retracted by a distance ΔZ, the XYscanning circuit 25 next drives the XYZ scanning piezoelectric element24 to move the probe only by ΔX in the X direction, and sets the probe21 at the next pixel position (3).

The surface structure of the specimen 11 is measured by the repeatedprobe 21 movement comprised of the above (1) (2) (3) steps. Whenscanning along the X direction is complete, the probe moves just aspecified distance ΔY in the Y direction, and again scans in the Xdirection. The specimen surface can be measured three-dimensionally byrepeating these movements.

The measurement of the atomic force gradient acting on the probe isdescribed next utilizing the block diagram of the lock-in amplifiershown in FIG. 4. The high frequency signal output from the oscillator 45is input to the exciter piezoelectric element 23 and the multiplier 41of the lock-in amplifier 40. The cantilever 22 is driven at a frequencyω by the exciter piezoelectric element 23. A laser beam 33 emitted fromthe semiconductor laser 31 is reflected by the cantilever 22, and isdetected by the position detector 32 made up of a dual-split orquad-split optical detector. The output from the force detector (laserposition detector circuit) 34 is multiplied by the output from theoscillator 45 at multiplier 41 inside the lock-in amplifier 40. Theamplitude of the frequency component output from the multiplier 41 viathe low-pass filter 42, that is synchronized with the oscillator signalis then detected.

When the probe 21 approaches near the surface of the specimen 11, andthe atomic force acts on the probe 21, the resonance point (frequency)of the cantilever 22 shifts. The lock-in amplifier 40 captures the shiftin this resonance point as a change in amplitude of the probe 21vibration. This amplitude change is detected as a fluctuation of theforce gradient, and when the preset change in the force gradient isreached, the probe 21 is determined to have arrived at the surface ofspecimen 11. The controller 37 then measures the coordinates of theprobe 21 at that time or in other words, measures the surface positioncoordinates (x, y, z).

FIG. 5 is graph showing the relation of the amount detected as thechange in amplitude by the lock-in amplifier and the distance betweenthe specimen surface and probe. The horizontal axis is the gap betweenthe probe and specimen. The vertical axis is the amplitude of thefrequency ω component detected by the lock-in amplifier. The curve Aexpresses the change in amplitude when the excitation frequency ω wasset to a frequency lower than the resonance frequency of probe 21. Inthis case, the amplitude of the frequency ω component increases when theprobe 21 nears the specimen surface. In the case of curve B, theamplitude of the frequency ω component conversely decreases when theprobe 21 nears the specimen surface. Therefore, by setting a threshold(value) for the amplitude change, the probe 21 can be decided to havereached the specimen surface when the detected change in amplitude hasexceeded that threshold.

When the position of the specimen surface is detected by means of theforce gradient acting on the probe 21, the XY scanning function iscompletely stopped by the XY scanning circuit 25. After measuring theprobe coordinates, the probe 21 is promptly retracted from the specimensurface in the Z direction by a specified distance ΔZ. After retractingin the Z axis direction, the probe 21 next moves to the next pixel pointby the XY scanning circuit 25 by distance ΔX. The probe 21 is then againmoved near the specimen 11 by the same procedure, and detects thesurface position. The surface position (x, y, z) of the specimen at eachpixel, and acquires information on the surface structure of thespecimen.

By driving the probe 21 in this way, the effects of friction due toscanning by continuous servo drive of the probe 2 can therefore beeliminated. The system can also be operated to detect an extremely smallforce, so errors due to the probe 21 slipping along a steep slope can bedrastically reduced when moving the probe 21 in proximity to thespecimen 11. The method of the present invention can therefore measurewith good accuracy the high aspect structures that will be needed in thefuture. The retraction amount ΔZ of probe 21 should preferably be setlarger than the height or depth of peaks or grooves on specimen 11, inview of the heights or depths of the surface structure of the specimen11.

In the example shown in the drawing, an optical lever was utilized fordetecting the displacement of the probe 21. However a capacitydisplacement meter, a strain gauge, or a light interferometer or similardevice of the known art in measuring technology may also be utilized.

Second Embodiment

FIG. 6 is a concept block diagram of showing another example of digitalprobing AFM in the present invention. In addition to the usual AFMstructure, this digital probing AFM contains an FM (frequencymodulation) detection type atomic force gradient detector.

In the example in the drawing, the force detector utilizes an opticallever system made up of a semiconductor laser 31, a position detector32, a force detector circuit 34. However in order to detect the forcegradient, the frequency is demodulated using a PLL (phase-lock-loop)circuit 50 and the change in the force gradient detected from the changein the frequency. The servo system, scanning system, proximitymechanism, and probe position detector identical to the first embodimentare utilized to regulate the detected signal to a fixed value. Unlikethe first embodiment, an external oscillator (or vibrator) is not usedfor self-vibrating the probe, instead a resonance circuit system in theinternal circuit network is utilized. In other words, the closed loopformed by the probe, exciter piezoelectric element 23, oscillatorcircuit 51, force detector 34 and optical lever probe position detector32 is made to function as a positive feedback coupling to make thecantilever 22 oscillate (vibrate) at the resonance point.

The measurement procedure is the same as the first embodiment. First ofall, a closed loop is formed by the probe, exciter piezoelectric element23, oscillator circuit 51, force detector 34 and light deflection probeposition detector 32. These components form a positive feedback couplingto make the cantilever 22 oscillate (vibrate) at the resonance point.The probe is made to approach near the specimen surface while beingvibrated. When the preset atomic force gradient acts on the probe, theprobe is determined to have made an approach near the specimen surface.The surface position information is then acquired and the probeafterwards retracted from the specimen surface to a specified distanceΔZ. At the Z position where the probe was retracted, the probe is movedin the X direction to the next pixel position, and the operation forsurface position measurement is repeated in the same way.

Measurement of the atomic force gradient acting on the probe isdescribed next utilizing the block diagram of PLL circuit shown in FIG.7. While being vibrated, the probe is made to approach near the surfaceof the specimen 11. The exciter signal from the oscillator circuit 51 isinput to the PLL circuit 50 at this time. The PLL circuit has ademodulation function, converts the resonance frequency into a lowfrequency signal, and inputs it to the servo circuit 35. In other words,the signal V₁ with the resonance frequency ω₁ from oscillator circuit 51equaling A cos ω₁ t, is multiplied by the signal V₂ (B cos ω₂t) with afrequency ω₂ from the voltage controlled oscillator 56 at the phasecomparator 53.

From the some component signals at the phase comparator 53, the loopfilter 54 selects and outputs a signal containing a low frequencycomponent of frequency (ω₁−ω₂), to the loop amplifier 55. The loopamplifier 55 outputs a signal G{cos(ω₁−ω₂)t} showing the change infrequency. The voltage controlled oscillator 56 is regulated so that(ω₂=ω₁){cos (ω₁−ω₂)t}, (G=ω₁) or in other words, so that ω₂ alwaysequals ω₁.

When the probe near the specimen surface, the atomic force is applied tothe probe, and the resonance point of the cantilever 22 is shifted. FIG.8 shows the change in resonant frequency detected by the PLL circuit 50,as the probe approaches the specimen surface. The fluctuation in theforce gradient is detected from this resonant frequency and when theamount of change in the force gradient reaches a preset amount, theprobe is determined to have reached the surface of the specimen 11. Thecontroller 37 thereupon promptly measures the surface position (x, y, z)of the specimen 11 from the probe position. The XY scanning function iscompletely stopped by the XY scanning circuit 25 at this time.

Instead of using an optical lever shown in the drawing for detecting thedisplacement of the probe, other measuring technology of the known artsuch as a capacity displacement meter, a strain gauge, or a lightinterferometer or similar device may be utilized.

Third Embodiment

FIG. 9 is a concept block diagram of a semiconductor scanning deviceutilizing a digital probing AFM incorporating the slope detectionmethod. The semiconductor scanning device shown in the figure containsan AFM having a function using the vibration method for detecting theatomic force gradient. This device further contains a chip positiondetection function for measuring at an optional measurement positionwithin the semiconductor chip, as well as a computer processing functionfor automatic measurements.

The force detector for the AFM utilizes the optical lever method. Thisforce detector is made up of a semiconductor laser 31, a positiondetector 32, and a force detector 34. A lock-in amplifier 40 detects theforce gradient the same as in the first embodiment. An approach device(not shown in drawing) is installed to make the probe 21 approach thesurface of the specimen 11 (semiconductor chip).

In addition to the AFM measurement means, this embodiment furthercontains an optical microscope 60 for simultaneously observing the probe21 and the specimen 11. The optical microscope 60 contains an objectivelens 61 and an eyepiece lens 62. This optical microscope 60 is capableof simultaneously observing the specimen surface and cantilever 22 andthe specimen 11. The epi-illumination system is omitted from thedrawings. A CCD camera 63 observes the illuminated specimen 11 and theprobe 2. The optical target captured by the CCD camera 63 is utilized toaccurately recognize the chip position in the system. The chip placementon the wafer and the positional relationship within the inspectiondevice are in this way calculated and found. Mapping in this way allowsaccurately determining the position of the probe 21 on locations on thechip whose surface shape was measured.

The controller 37 communicates (exchanges data) with the host computerand the wafer auto conveyor robot, receives measurement points andmeasurement conditions, controls automatic measurement and/or controlscarry-in/carry-out of wafers from the robot. The controller 37 instructsthe XY scanning circuit 25 to drive the specimen stage 12 and the XYZscanning piezoelectric element 24 so that the location specified by thehost computer becomes the observation position, and measures thespecified location. The controller 37 communicates (transfers) themeasurement data to the host computer and displays it on the displaydevice 38.

The present invention as described above, when used to measure theshapes of high aspect structures with dimensions in the submicron range,is capable of making measurements down to the nanometer range and belowwithout the probe slipping on the oblique surface. The present inventioncan further be utilized for defect (flaw) measurement and measuringdimensions of tiny devices. The present invention can also be utilizedas a line monitor for semiconductor processes.

INDUSTRIAL APPLICABILITY

The present invention configured as described above, is capable ofmaking measurements down to the nanometer range and below with noslipping of the probe on oblique surfaces in the measuring of shapes ofhigh aspect structures with dimensions in the submicron range.

1-10. (canceled)
 11. A scanning probe microscope comprising: a specimenstage for mounting the specimen, a probe, a cantilever for supportingthe probe, a first probe movement means for moving the probetwo-dimensionally along the surface of the specimen, a second probemovement means for moving the probe closer to or farther away from thespecimen surface, a probe position detection means for detecting theprobe position, a means to oscillate the cantilever at a specifiedfrequency shifted slightly from the cantilever resonance point, anamplitude detection means to detect the oscillation amplitude of thespecified frequency component of the cantilever, and a control means todetect changes in the vibration amplitude while moving the cantilevercloser to the specimen surface and measure the probe position when thechange in the vibration amplitude has reached a specified quantity. 12.A scanning probe microscope according to claim 1, wherein the amplitudedetection means is comprised of a lock-in amplifier.
 13. A scanningprobe microscope comprising: a specimen stage for mounting the specimen,a probe, a cantilever for supporting the probe, a first probe movementmeans for moving the probe two-dimensionally along the surface of thespecimen, a second probe movement means for moving the probe closer toor father away from the specimen surface, a probe position detectionmeans for detecting the probe position, a means to oscillate thecantilever to which the probe is attached at its resonance point, ameans to detect a change of the resonance of the cantilever, and acontrol means to detect a shift in the resonance frequency of thecantilever while moving the cantilever in a direction closer to thespecimen surface, and measure the probe position when the shift in theresonance frequency reaches a specified quantity.
 14. A scanning probemicroscope according to claim 3, wherein the means to detect a change ofthe resonance of the cantilever being a resonance frequency shiftdetection means to detect a shift in the resonance frequency of thecantilever.
 15. A scanning probe microscope according to claim 4, wherein the resonance frequency shift detection means is a phase locked loopcircuit.
 16. A scanning probe microscope according to claim 1, whereinthe probe is comprised of carbon nanotube.
 17. A scanning probemicroscope according to claim 3, wherein the probe is comprised ofcarbon nanotube.
 18. A scanning probe microscope according to claim 1,wherein a capacity displacement meter, a strain gauge, a lightinterferometer or an optical lever may be utilized as the probe positiondetection means.
 19. A scanning probe microscope according to claim 3,wherein a capacity displacement meter, a strain gauge, a lightinterferometer or an optical lever may be utilized as the probe positiondetection means.
 20. A specimen surface structure measuring method formeasuring the surface structure of the specimen utilizing the scanningprobe microscope containing a probe attached on a cantilever, the methodcomprising the steps of: stopping the servo control for maintaining afixed gap between the probe and specimen surface and moving the probealong the specimen surface to the measurement point with the probeseparate from the specimen, moving the probe closer to the specimensurface and measure the probe position when a specified atomic force isdetected in an atomic force region, and moving the probe away from thespecimen surface immediately after the measurement, in which these stepsare repeated at each measurement point.
 21. A specimen surface structuremeasuring method according to claim 10, wherein in the step for movingthe probe away from the specimen surface, the probe is moved at least toa distance where there is no absorption force to attract the probe. 22.A specimen surface structure measuring method according to claim 10,wherein the vibration frequency is a frequency shifted slightly from thecantilever resonance point, and the specified atomic force is detectedbased on the change in the vibration amplitude of the cantilever.
 23. Aspecimen surface structure measuring method according to claim 11,wherein the vibration frequency is a frequency shifted slightly from thecantilever resonance point, and the specified atomic force is detectedbased on the change in the vibration amplitude of the cantilever.
 24. Aspecimen surface structure measuring method according to claim 10,wherein the vibration frequency is the frequency of the cantileverresonance point, and the specified atomic force is detected based on theshift in the cantilever resonance frequency.
 25. A specimen surfacestructure measuring method according to claim 11, wherein the vibrationfrequency is the frequency of the cantilever resonance point, and thespecified atomic force is detected based on the shift in the cantileverresonance frequency.